JPS601740A - Rotary anode x-ray tube - Google Patents

Abstract

PURPOSE:To practically use a magnetic bearing type rotary anode x-ray tube by additionally use a pivot bearing that can fully be resistant to ultrahigh speed rotation in the magnetic bearing and separately providing a mechanical bearing for exclusive use that performs the required high temperature low speed rotation in the degassing exhaust process. CONSTITUTION:A rotary frame body 13 is provided at a part of a rotor 4 and a vacuum sealing frame body 14 is provided at a part of a vacuum container 1. Both form a pivot bearing 15 that can be resistant to the coaxial ultrahigh speed rotation with a magnetic bearing. While both are being operated as x-ray tubes, they are made to elastically touch each other and anode current is induced through the contact. On the other hand, in the exhaust process, a protrusion section 16 provided at a part of the rotary frame body 13 engages with a ball bearing 17 provided at a part of the vacuum sealing frame body 14 and is supported so as freely rotate. The rotation can be started only by applying a weak rotary magnetic field from the outside of the vacuum container 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a rotating anode X-ray tube, and particularly to a rotating anode X-ray tube that employs a magnetic bearing for the purpose of ultra-high speed rotation.

[Background of the invention]

In conventional X-ray tubes, as described in Japanese Utility Model Publication No. 57-28391, for example, the anode in the vacuum envelope is supported by a mechanical ball bearing, and during operation as an X-ray tube, It is used by rotating it by applying a rotating magnetic field from outside the vacuum envelope.

Such mechanical ball bearing type X-ray tubes have been used with an anode rotation speed of 3,000 to 20,000 rpm, but rotations of more than s20)000 rprn cause material damage due to the frictional heat of the ball bearings. leading to slowdown,
X-ray tubes used in medical settings, in particular, cannot be put to practical use because they are subject to severe wear and cannot have a long service life, and as the rotational speed increases, they become extremely noisy. Practical examples at rotational speeds of ,000 rpm or higher are extremely rare.

On the other hand, from the perspective of improving the quality of X-ray images, small-focus X-ray tubes are required, and at the same time, there is a need for rapid imaging of moving subjects. Improving the surface speed, that is, the anode rotation speed, is becoming an urgent issue, and from this perspective, the introduction of magnetic bearings is considered as an alternative to the conventional mechanical ball bearing system as described above. .00Or
There is an urgent need to put this technology into practical use, with the goal of achieving an anode rotation speed of pm.

However, since magnetic bearings essentially place the anode in a floating state in a high-vacuum container without contact and rotate it at ultra-high speed, the anode current cannot be drawn out of the vacuum container as it is. It's impossible. In addition, in the process of creating a high vacuum inside the X-ray tube, there is a process of degassing the tube's internal electrode parts, namely the anode and cathode, by heating them to over 900°C for a long time. A well-known method is to attach the easy-to-use cathode side to the exhaust vacuum system, rotate it at low speed with the anode positioned vertically upward, and irradiate the cathode with an electron beam from the outside to heat and degas it. However, due to the lack of heat resistance of the magnetic bearing coil and the inability to ensure high voltage resistance, the exhaust process for degassing cannot be carried out sufficiently. There was a bottleneck.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and its purpose is to provide a magnetic bearing type rotating anode X-ray tube that overcomes the bottlenecks regarding anode current derivation and degassing process and enables practical use. It is in.

[Summary of the invention]

In order to achieve these objectives, the present invention combines a magnetic bearing with a pivot bearing that can sufficiently withstand ultra-high speed rotation for deriving anode current, and also uses a pivot bearing that can sufficiently withstand ultra-high speed rotation for degassing and exhausting. A special mechanical bearing is separately provided to perform this operation without the aid of a magnetic bearing.

[Embodiments of the invention]

First, the concept of a magnetic bearing type rotating anode X-ray tube will be explained using FIG.

In FIG. 1, a cathode 3 that emits an electron beam 2, a rotor 4 that constitutes a rotating anode, a target 5, and a rotor 4 that is connected to a cathode 3 that emits an electron beam 2, a rotor 4 that constitutes a rotating anode, and a target 5 are placed inside a glass vacuum container 1 that serves as a high vacuum insulating envelope. A rotating shaft 6 that transmits the rotation of the target 5 to the target 5 is housed therein. The electron beam 2 emitted from the cathode 3 gives energy to the target 5 which rotates at an extremely high speed, and X-rays 8 are emitted to the outside through the X-ray emission window 7.

The vacuum container 1 is placed in a container 9 as an envelope of an X-ray tube device with an insulating oil 10 in between. On the other hand, the rotation of the anode is realized by applying a high frequency rotating magnetic field to the gerotor 4 using the rotating coil 11.
It exists inside the vacuum vessel 1 in a suspended form due to the magnetic field applied by the position coil 12 without coming into contact with anything else. That is, the rotating anode part rotates at high speed in a floating state, and its position in the axial and radial directions is fixed by the position coil 1.
Achieved by 2.

In this case, current must flow between the cathode 3 and the anode section, that is, the target 5, the rotating shaft 6, and the rotor 4, but when the rotating anode is rotating in a floating state,
The current cannot be derived, that is, the electron beam does not flow. In addition, in the process of connecting the vacuum vessel 1 containing the cathode 3 and the anode part to an external evacuation system and evacuating it, unless the position coil 12 operates, the anode part cannot maintain its 4- position and the vacuum vessel collapses. 1 or the cathode 3. In an X-ray tube that operates at a high voltage, generally the cathode 3 is
A high vacuum is obtained by degassing a part of the vacuum vessel 1 by connecting a part of the vacuum vessel 1 to an external vacuum evacuation system while applying power several times higher than during normal X-ray tube operation to make the target 5 red-hot.
In that case, the target 5 directly irradiated with the electron beam 2
Not only that, but also the rotating shaft 6 and rotor 4 become hot, so the position coil 12, which is not cooled by the insulating oil 10 as it is when the X-ray tube is in operation, has heat dissipated from the rotor 4 at a rate higher than that during the X-ray tube operation. Since it may double in size, it cannot be used due to heat resistance issues, and as a result, it becomes impossible to maintain the position of the anode.

In order to solve such problems, in the embodiment of the present invention shown in FIG. Together, they form a pivot bearing 15 that is coaxial with the magnetic bearing and can withstand ultra-high speed rotation. During operation as an X-ray tube, the two come into elastic contact due to the action of the position coil 12 similar to that shown in FIG. 1, and an anode current is derived through this contact.

On the other hand, during the exhaust process, if the cathode 3 is stood vertically with the cathode 3 facing downward, the anode will fall due to gravity, but the rotating structure 1
A protrusion 16 provided on a part of the vacuum sealing structure 14 fits into a ball bearing 17 provided on a part of the vacuum sealing structure 14 and is rotatably supported, preventing further fall and preventing the vacuum container 1 from falling further. Rotation can be started simply by applying a weak rotating magnetic field from the outside, and by irradiating the target 5 with the Muroko beam 2 during exhaust, rotational irradiation heating can be performed while suppressing target surface roughening and melting that are likely to occur.

〔Effect of the invention〕

As explained above, according to the present invention, by using a pivot bearing in combination with a magnetic bearing, it is possible to derive an anode current, and when the cathode side is facing down, it supports the anode part and enables low-speed rotation. By separately installing a special mechanical bearing for this purpose, the degassing process while rotating at high temperature and low speed can be performed without using a magnetic bearing, which has led to the practical application of magnetic bearing type rotating anode X-ray tubes. It becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a sectional view for explaining the concept of a magnetic bearing type rotating anode X-ray tube, and FIG. 2 is a sectional view showing details of an anode rotating structure showing an embodiment of the present invention. 1. Fist/vacuum container, 2. Monkey/electron beam, 3. Φ.
Φ cathode, 4... rotor, 5... target,
6...Fist/rotating shaft, 11@...Rotating coil, 12...
...Position coil, 13.Fist...Rotating structure, 14...
Vacuum sealed structure, 15Φ...Pivot bearing, 16...
Fist protrusion, 17...Ball bearing.

Claims (1)

[Claims] A rotating device comprising a cathode section for electron emission, an anode section placed opposite to the cathode section, and a magnetic bearing that allows the anode section to float in a vacuum tube and enable ultra-high speed rotation. In the anode X-ray tube, there is a pivot bearing for deriving the anode current, which is arranged coaxially with the magnetic bearing, and when the X-ray tube is arranged vertically with the cathode section facing downward and the magnetic bearing is removed, the anode section What is claimed is: 1. A rotating anode X-ray tube comprising a mechanical bearing that rotatably supports the anode, prevents the anode from falling, and enables low-speed rotation in that state.